Device for controlling electromagnetically operated valves in an electrohydraulic brake system

ABSTRACT

The present invention relates to a device for controlling electromagnetically operable valves of an electrohydraulic brake system for motor vehicles of the ‘brake-by-wire’ type having an electronic control or regulation unit that comprises at least one valve driver stage.  
     In order to ensure maximum possible availability of the electronically controlled system functions, especially with a view to achieving a short stopping distance and a sufficient degree of vehicle stability regardless of the vehicle type or of whether the vehicle is loaded or unloaded, according to the present invention, the control and regulation unit ( 26 ) includes two additional valve driver stages ( 32, 33 ) associated with which is a first and a second group of valves ( 11,13,14, 17,18, 27,28,34,35,37,38 ), the said driver stages being used to disable the first or the second group when malfunction occurs.

TECHNICAL FIELD

[0001] The present invention generally relates to a device forcontrolling valves and more particularly relates to a device forcontrolling electromagnetically operable valves of an electrohydraulicbrake system for motor vehicles.

BACKGROUND OF THE INVENTION

[0002] International patent application WO 00/68053 discloses a brakesystem of this general type. The mentioned publication, however, doesnot provide any the failure probability of the actuation of theelectromagnetically operable valves employed.

SUMMARY OF THE INVENTION

[0003] In view of the above, an object of the present invention is todisclose a device for actuating electromagnetically operable valves ofan electrohydraulic brake system of the type mentioned hereinabove, saiddevice ensuring maximum possible availability of the electronicallycontrolled system functions, especially with a view to achieving a shortstopping distance and a sufficient degree of vehicle stabilityregardless of the vehicle type or of whether the vehicle is loaded orunloaded.

[0004] This object is achieved by the present invention because thecontrol and regulation unit includes two additional valve driver stagesassociated with which is a first and a second group of valves, the saiddriver stages isolating said group in addition from the supply voltageor mass, with a view to ensuring thereby the disabling of the first orthe second group also when malfunction occurs.

[0005] The present invention includes, in a first embodiment, a firstvalve driver stage for driving the separating valves and for driving thepressure control valves respectively associated with a brake of a firstor a second vehicle axle. The present invention also includes a secondvalve driver stage for driving pressure-compensating valves and pressurecontrol valves associated with the other two wheel brakes of the firstor the second vehicle axle. The mentioned variant permits an electronicbrake pressure control on each of the four vehicle wheels.

[0006] A second embodiment of the present invention is that the firstvalve driver stage is coupled to the separating valve of a first vehicleaxle, the pressure-compensating valve of a second vehicle axle, and thepressure control valves being associated with respectively one brake ofthe first or the second vehicle axle, while the second valve driverstage is provided for the separating valve of the second vehicle axle,the pressure-compensating valve of the first vehicle axle, and thepressure control valves being associated with the other two brakes ofthe first or the second vehicle axle. This variant allows an electronicbrake pressure control of three wheels, while the master brake cylinderfurnishes the brake pressure for the wheel brake associated with thefourth wheel.

[0007] Finally, a third embodiment of the present invention includescoupling the first valve driver stage to the separating valve and thepressure-compensating valve as well as the pressure control valves ofwheel brakes associated with a first vehicle axle, while the secondvalve driver stage is provided for the separating valve and thepressure-compensating valve as well as the pressure control valves ofwheel brakes associated with a second vehicle axle. This allocationallows an electronic brake pressure control of two wheels, while thepressure introduced by the driver into the master brake cylinder isapplied to the wheel brakes of the other wheels.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a simplified circuit diagram of a design of theelectrohydraulic brake system of the present invention.

[0009]FIG. 2 is a second alternative of actuating the electromagneticvalves in an electrohydraulic brake system according to FIG. 1.

[0010]FIG. 3 is a third alternative of actuating the electromagneticvalves in an electrohydraulic brake system according to FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The electrohydraulic brake system illustrated in the drawingsessentially comprises a dual-circuit master brake cylinder or tandemmaster cylinder 2 that is operable by means of an actuating pedal 1,cooperates with a pedal travel simulator 3 and includes two pressurechambers isolated from one another and being in communication with anon-pressurized pressure fluid supply reservoir 4. Wheel brakes 7, 8e.g. associated with the rear axle are connected to the first pressurechamber (primary pressure chamber) by means of a closable firsthydraulic line 5, with wheel brake 7 being associated with the left rearwheel and wheel brake 8 being associated with the right rear wheel. Line5 is closed by means of a first separating valve 11, while in a lineportion 12 between the wheel brakes 7, 8 an electromagneticallyoperable, preferably normally open (NO) pressure-compensating valve 13is inserted which enables brake pressure control on each individualwheel, if required.

[0012] The second pressure chamber of the master brake cylinder 2, towhich a pressure sensor 15 can be connected, is connectable to the otherpair of wheel brakes 9, 10 associated with the front axle by way of asecond hydraulic line 6 closable by means of a second separating valve14, with wheel brake 9 being associated with the left front wheel andwheel brake 10 being associated with the right front wheel. Again, anelectromagnetically operable, preferably normally open (NO)pressure-compensating valve 19 is inserted into a line portion 16disposed between the wheel brakes 9, 10. Because the design of thehydraulic circuit connected to the second pressure chamber of the masterbrake cylinder 2 is identical with the brake circuit 11 that isexplained in the preceding description, it need not be discussed in thefollowing text.

[0013] A high-pressure accumulator 21 is used as the above-mentionedauxiliary pressure source, said accumulator being filled with pressurefluid under high pressure by a motor-and-pump assembly 20. Themotor-and-pump assembly 20 comprises a pump 23 driven by means of anelectric motor 22 as well as a pressure limiting valve 24 connected inparallel to said pump 23. The suction side of the pump 23 is connectedto the above-mentioned pressure fluid supply reservoir 4 by way of anon-return valve. A pressure sensor 25 monitors the hydraulic fillingpressure of the high-pressure accumulator 21 generated by the pump 23.

[0014] As can further be taken from the drawings, two electromagnetic,normally closed two-way/two-position directional control valves 17, 18of analog operation are associated with the wheel brakes 7, 8 of thevehicle rear axle, said valves fulfilling the function of inlet valvesthat are required for electrohydraulically controlled braking operationsand the inlet ports of which are connected to the above-mentionedhigh-pressure accumulator 21. Further, the wheel brakes 7, 8 areconnected to a third hydraulic line 39 by way of each oneelectromagnetic, normally closed two-way/two-position directionalcontrol valve or outlet valve 27, 28 of analog operation, said line 39being in communication with the non-pressurized pressure fluid supplyreservoir 4, on the other hand. The hydraulic pressure prevailing in thewheel brakes 7, 8 is determined by means of each one pressure sensor 30,31. The wheel brakes 9, 10 associated with the vehicle front axlecooperate similarly with valve pairs 34, 37 and 35, 38, respectively,with pressure control valves 34, 35 fulfilling the function of the inletvalves and pressure control valves 37, 38 fulfilling the function of theoutlet valves.

[0015] An electronic control unit 26 is used for the joint actuation ofthe motor-and-pump assembly 20 as well as the electromagnetic valves 11,13, 14, 17, 18, 19, 27, 28, 34, 35, 37, 38. The output signals of anactuating travel sensor 36, preferably of redundant design andcooperating with the actuating pedal 1, and of the above-mentionedpressure sensor 15 are sent as input signals to said control unit 26,thereby permitting a detection of the driver's deceleration demand.However, other means such as a force sensor sensing the actuating forceat the actuating pedal 1 may also be used for the detection of thedriver's deceleration demand. As further input quantities, the outputsignals of the pressure sensors 25, 30, 31 as well as the output signalsof wheel sensors (only represented) representative of the speed of thevehicle are sent to the electronic control unit 26.

[0016] As is indicated in FIG. 1 only schematically, the electroniccontrol unit 26 among others comprises a valve driver stage 29 and twoadditional valve driver stages 32, 33, the purpose of which is explainedin the following text.

[0017] To ensure maximum possible availability of the electronicallycontrolled system functions of the illustrated electrohydraulic brakesystem, the above-mentioned electromagnetically operable valves aresubdivided into two groups and associated with the two additional valvedriver stages 32, 33. Thus, the group associated with the firstadditional valve driver stage 32 is composed of the two separatingvalves 11, 14, the pressure control valves 34, 37 of the wheel brake 9associated with the left front wheel, and the pressure control valves18, 28 of the wheel brake 8 associated with the right rear wheel. Incontrast thereto, the group associated with the second additional valvedriver stage 33 is composed of the two pressure-compensating valves 13,19, the pressure control valves 35, 38 of the wheel brake 10 associatedwith the right front wheel as well as the pressure control valves 17, 27of the wheel brake 7 associated with the left rear wheels.

[0018] Upon failure of the first additional valve driver stage 32 or oneof the drivers of the associated valve group, said failure requiringsubsequent closure of the pressure-compensating valves 13, 19, it isstill possible to electronically control the brake pressures in thewheel brake 10 associated with the right front wheel and the wheel brake7 associated with the left rear wheel. A hydraulic through grip effectedby the driver by way of his/her actuating or pedal force acting upon themaster brake cylinder 2 can produce the brake pressures in the wheelbrake 9 associated with the left front wheel and in the wheel brake 8associated with the right rear wheel.

[0019] Upon failure of the second additional valve driver stage 33 orone of the drivers of the associated valve group, the two separatingvalves 11, 14 can become closed. Since both pressure-compensating valves13, 19 remain open, the brake pressures in all four wheel brakes 7-10can be controlled electronically because the front axle is controlled byway of the valve pair 34, 37 and the rear axle by way of the valve pair18, 28.

[0020] In the second example being shown in a greatly simplified view inFIG. 2, the group associated with the first additional valve driverstage 32 is composed of the separating valve 14 associated with thevehicle front axle, the pressure control valves 34, 37 of the wheelbrake 9 associated with the left front wheel, the pressure-compensatingvalve 13 associated with the vehicle rear axle, as well as the pressurecontrol valves 17, 27 of the wheel brake 7 associated with the left rearwheel. In contrast thereto, the group associated with the secondadditional valve driver stage 33 is composed of the separating valves 11associated with the vehicle rear axle, the pressure control valves 18,28 of the wheel brake 8 associated with the right rear wheel, thepressure-compensating valve 19 associated with the vehicle front axle aswell as the pressure control valves 35, 38 of the wheel brake 10associated with the right front wheel.

[0021] Upon failure of the first additional valve driver stage 32 or oneof the drivers of the associated valve group, said failure requiringsubsequent closure of the pressure-compensating valve 19 associated withthe vehicle front axle and the separating valve 11 associated with thevehicle rear axle, it is still possible to electronically control thebrake pressures in the wheel brake 10 associated with the right frontwheel and the wheel brakes 7, 8 associated with the rear vehicle axle. Ahydraulic through grip effected by the driver by way of his/heractuating or pedal force acting upon the master brake cylinder 2 canproduce the brake pressure in the wheel brake 9 associated with the leftfront wheel.

[0022] Upon failure of the second additional valve driver stage 33 orone of the drivers of the associated valve group, said failure requiringsubsequent closure of the pressure-compensating valve 13 associated withthe vehicle rear axle and the separating valve 14 associated with thevehicle front axle, it is still possible to electronically control thebrake pressures in the wheel brake 7 associated with the left rear wheeland the wheel brakes 9, 10 associated with the vehicle front axle. Ahydraulic through grip effected by the driver by way of his/heractuating or pedal force acting upon the master brake cylinder 2 canproduce the brake pressure in the wheel brake 8 associated with theright rear wheel.

[0023] In the third example being shown in a greatly simplified view inFIG. 3, the group associated with the first additional valve driverstage 32 is composed of the separating valve 14 associated with thevehicle front axle, the pressure-compensating valve 19 associated withthe vehicle front axle as well as the pressure control valves 34, 37,35, 38 of the wheel brakes 9, 10 associated with the vehicle front axle.In contrast thereto, the group associated with the second additionalvalve driver stage 33 is composed of the separating valve 11 associatedwith the vehicle rear axle, the pressure-compensating valve 13associated with the vehicle rear axle as well as the pressure controlvalves 17, 27, 18, 28 associated with the wheel brakes 7, 8 of thevehicle rear axle.

[0024] Upon failure of the first additional valve driver stage 32 or oneof the drivers of the associated valve group, it is possible toelectronically control the brake pressures in the wheel brakes 7, 8associated with the vehicle rear axle without restrictions. A hydraulicthrough grip effected by the driver by way of his/her actuating or pedalforce acting upon the master brake cylinder 2 can produce the brakepressure in the wheel brakes 9, 10 associated with the vehicle frontaxle.

[0025] Upon failure of the second additional valve driver stage 33 orone of the drivers of the associated valve group, it is possible toelectronically control the brake pressures in the wheel brakes 9, 10associated with the vehicle front axle without restrictions. A hydraulicthrough grip effected by the driver by way of his/her actuating or pedalforce acting upon the master brake cylinder 2 can produce the brakepressure in the wheel brakes 7, 8 associated with the vehicle rear axle.

[0026] As can be taken from FIGS. 2 and 3, in particular, the additionalvalve driver stages 32, 33 are connected in each case between thecorresponding valve group and the positive pole of a vehicle battery(only represented). It is, however, also feasible to interconnect theadditional valve driver stages 32, 33 between the corresponding valvegroup and the vehicle mass.

1. Device for controlling electromagnetically operable valves of anelectrohydraulic brake system for motor vehicles, which device in a‘brake-by-wire’ operating mode is controllable by the vehicle operatoras well as irrespective of the vehicle operator and can be operated in afallback operating mode allowing only operation by the vehicle operator,including a device for detecting a driver's request for deceleration, anemergency pressure generator or master brake cylinder operable by meansof a brake pedal and including at least one pressure chamber, associatedwith which generator is a non-pressurized pressure fluid supplyreservoir, a hydraulic auxiliary pressure source whose pressure can beapplied to wheel brakes that are connectable to the master brakecylinder by way of hydraulic connections closable by means ofelectromagnetically operable separating valves, and associated withwhich are electromagnetically operable pressure control valves (inletvalve, outlet valve) that connect the wheel brakes to the pressuresource in a pressure increase phase, are or become closed in a pressuremaintaining phase and connect the wheel brakes to the pressure fluidsupply reservoir in a pressure reduction phase, electromagneticallyoperable pressure-compensating valves that permit a pressurecompensation between the wheel brakes of a vehicle axle, as well as anelectronic control and regulation unit for actuating the auxiliarypressure source, the at least one separating valve, the pressure controlvalves and the pressure-compensating valves, said unit including atleast one valve driver stage, characterized in that the control andregulation unit (26) includes two additional valve driver stages (32,33) associated with which is a first and a second group of valves(11,13,14,17,18,27,28,34,35,37,38), the said driver stages being used todisable the first or the second group, respectively, when malfunctionoccurs.
 2. Device as claimed in claim 1, characterized in that the firstvalve driver stage (32) is meant for the separating valves (11, 14) andfor the pressure control valves (34, 37 or 18, 28) respectivelyassociated with a brake (9 or 8) of a first or a second vehicle axle,while the second valve driver stage (33) is provided for thepressure-compensating valves (13, 19) and the pressure control valves(35, 38 or 17, 27) associated with the other two wheel brakes (10 or 7)of the first or the second vehicle axle.
 3. Device as claimed in claim1, characterized in that the first valve driver stage is provided forthe separating valve (14) of a first vehicle axle, thepressure-compensating valve (13) of a second vehicle axle and thepressure control valves (34, 37 or 17, 27) being associated withrespectively one brake (9 or 7) of the first or the second vehicle axle,while the second valve driver stage is provided for the separating valve(11) of the second vehicle axle, the pressure-compensating valve (19) ofthe first vehicle axle and the pressure control valves (35, 38 or 18,28) being associated with the other two brakes (10 or 7) of the first orthe second vehicle axle.
 4. Device as claimed in claim 1, characterizedin that the first valve driver stage is provided for the separatingvalve (14) and the pressure-compensating valve (19) as well as thepressure control valves (34, 37 or 35, 38) of wheel brakes (9, 10)associated with a first vehicle axle, while the second valve driverstage is provided for the separating valve (11) and thepressure-compensating valve (13) as well as the pressure control valves(17, 27 or 18, 28) of wheel brakes (7, 8) associated with a secondvehicle axle.